Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedure. This test is intended to diagnose the following:

• HO2S and heater.
• HO2S and sensor connection.
• Vacuum systems.
• Fuel injector and/or fuel injector circuitry.
• PCM.
• HO2S HTR, HO2S, HO2S INJ 1-6 and VPWR harness circuits.
  NOTE: HO2S may be displayed as O2S on tester.

1. 1) DTC P0130: HO2S Circuit Malfunction
   
   DTC P0130 indicates an irrational value in upstream HO2S circuit. Possible causes for fault are as follows:
   • Damaged upstream HO2S or circuit.
   • Intake air system malfunction.
   • Fuel system malfunction.
   • Exhaust system leak.
   • Ignition system malfunction.
   • PCV malfunction.

   Turn ignition off. Connect New Generation Star (NGS) tester to DLC. Start and warm engine to normal operating temperature. Using NGS tester, access HO2S PIDs. Operate engine at different speeds while observing HO2S PID. If HO2S PID is not constantly varying between .33-0.99 volt, go to next step. If HO2S PID is .33-0.99 volt and constantly varying, turn ignition off. If diagnosing DTCs P0131, P0132, P0133 or P1148, go to step  20). If any other DTC is being diagnosed, go to TEST Z  or see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - VILLAGER article for intermittent diagnostic procedure.

   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1)  to step 11)  . No test procedures have been omitted.
2. 11) Check HO2S Output Voltage
   
   Using NGS tester, access HO2S PIDs. Start engine and observe HO2S PID voltage readings while accelerating engine up to 2000 RPM. If HO2S increases to greater than .5 volt, go to step  14). If HO2S does not increase to greater than .5 volt, go to next step.
3. 12) Check HO2S Circuit Continuity
   
   Turn ignition off. Disconnect suspect HO2S connector. Disconnect PCM harness connector. Inspect connector for damaged pins and repair if necessary. Measure resistance of HO2S11 or HO2S12 circuits between HO2S harness connector and PCM harness connector. See Fig 1. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, repair open in circuit.
   Fig 1: Identifying HO2S Circuits & Connector Terminals

   Courtesy of FORD MOTOR CO.
4. 13) Check HO2S Signal Short To Ground
   
   Measure resistance between HO2S11 and/or HO2S12 and GND circuits at PCM harness connector. If resistance is not greater than 10 k/ohms repair short to ground in circuit. If resistance is greater than 10 k/ohms, go to step  40).
5. 14) Check For Short To Power
   
   Measure resistance between HO2S11 or HO2S12 and KAPWR circuit at PCM harness connector. If resistance is not greater than 10 k/ohms, repair short in circuit. If resistance is greater than 10 k/ohms, go to next step.
6. 15) Erase DTCs
   
   Connect all disconnected components. Erase all DTCs. See CLEARING CODES . Operate engine at 1500-2000 RPM for greater than 3 minutes. Repeat QUICK TEST . If DTC does not reset, fault is intermittent. See TEST Z  for intermittent fault diagnosis. If diagnosing DTCs P0131, P0132, P0133, or P1148, go to next step. If diagnosing any other DTC, replace damaged HO2S. If DTC is still present, replace PCM.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15)  to step 20)  . No test procedures have been omitted.
7. 20) DTC P0135 & P0141: Heater Circuit Malfunction
   
   DTC P0135 indicates a malfunction in upstream oxygen sensor heater circuit. DTC P0141 indicates a malfunction in downstream oxygen sensor heater circuit. Possible causes for malfunction are as follows:
   • Faulty or damaged HO2S.
   • Poor harness connection.
   • Open or short in heater circuit.
   • Open heater GND circuit.
   • Faulty PCM.

   Examine HO2S harness connectors for damage or corrosion. Repair connectors as necessary. If HO2S harness connectors are okay, go to step  22).

   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 20)  to step 22)  . No test procedures have been omitted. Step 22)  may generate unrelated DTCs. Clear all DTCs after this step.
8. 22) Check Appropriate HO2S Heater Circuit
   
   Disconnect HO2S11 or HO2S12 harness connectors. Connect DVOM between ground and HTR11 or HTR12 circuits at appropriate HO2S harness connector. Start engine and monitor heater voltage. Voltage will be high (battery voltage) with heater off and low (less than one volt) with heater on. Heater voltage should be high for 5 seconds (heater off) after engine start, then stay low (heater on) at idle. Increase engine speed to greater than 4200 RPM. Heater voltage should be high (heater off) at greater than 4200 RPM, then stay low (heater on) at less than 4200 RPM. If heater voltage stays high for 5 seconds after engine start, becomes low at idle and changes to high at greater than 4200 RPM, go to step  24). If voltage stays high, go to step  24). If voltage stays low, go to next step.
9. 23) Check HO2S Heater Circuit For Short To Ground
   
   Measure resistance between HTR11 or HTR12 and GND circuits at PCM harness connector. If resistance is greater than 10 k/ohms, go to next step. If resistance is not greater than 10 k/ohms, repair short in circuit.
10. 24) Check VPWR Circuit Continuity
    
    Turn ignition on. Measure voltage between ground and VPWR circuit of appropriate HO2S harness connector. See Fig 1. If voltage is greater than 10 volts, go to next step. If voltage is not greater than 10.5 volts, repair open in circuit.
11. 25) Check HO2S Heater Circuit Continuity
    
    Measure resistance of appropriate HTR circuit between HO2S harness connector and PCM harness connector. See CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, repair open in circuit.
12. 26) Check HO2S Heater
    
    Measure resistance between HTR and VPWR circuits at HO2S harness connector. If resistance is not about 6 ohms, replace HO2S. If resistance is about 6 ohms, replace PCM.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 26)  to step 40)  . No test procedures have been omitted.
13. 40) DTC P0171 & P0172: Fuel Trim Malfunction
    
    DTC P0171 indicates air/fuel ratio too lean. DTC P0172 indicates air/fuel ratio too rich. Possible causes for malfunction are as follows:
    • Excessive fuel pressure.
    • Leaking fuel injector(s).
    • Leaking fuel pressure regulator.
    • Low fuel pressure.
    • Restricted fuel injectors.
    • Faulty HO2S or circuit.
    • Induction system air leaks.
    • Restricted air filter.
    • Faulty PCV system.
    • Engine mechanical problem.
    • Oil level over full.
    • Ignition system malfunction.

    If any of the listed areas are faulty, repair as necessary. If all of the listed areas are okay, go to next step.

14. 41) Fuel Delivery System
    
    Connect fuel pressure gauge to fuel rail or fuel filter. Start engine and observe fuel pressure. If fuel pressure is 34-43 psi (234-294 kPa), go to next step. If fuel pressure is not as specified, go to TEST HC .
    NOTE: Before performing following test, determine whether misfire DTCs are displayed with fuel control DTCs. Use misfire DTCs to determine injector circuits requiring testing.
15. 42) Check Injector Harness & Resistance
    
    Disconnect PCM. Measure resistance of suspect injector between injector and PCM KAPWR circuit terminal No. 80 (Yellow wire) at PCM harness connector. See CIRCUIT PIN IDENTIFICATION  table. If resistance is 10-14 ohms, injector and harness resistance are okay. Go to step  45). If resistance is not 10-14 ohms, go to next step.
16. 43) Check Injector Circuit Continuity
    
    Turn ignition off. Disconnect injector harness connector. Measure resistance of KAPWR circuit between injector harness connector and PCM harness connector. Measure resistance of injector signal circuit between injector connector and PCM harness connector. See Fig 2. See CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, repair open circuit.
    Fig 2: Identifying Fuel Injector Circuits & Connector Terminals

    Courtesy of FORD MOTOR CO.
17. 44) Check Injector Harness Circuit For Short To Power Or Ground
    
    Measure resistance between injector signal and KAPWR, GND and SIG RTN circuits at PCM harness connector. See CIRCUIT PIN IDENTIFICATION  table. Measure resistance between injector signal circuit and ground at PCM harness connector. If each resistance measurement is greater than 10 k/ohms, go to next step. If each resistance measurement is not greater than 10 k/ohms, repair short in circuit.
18. 45) Check Injector Driver Signal
    
    Reconnect PCM harness connector. Connect a standard non-powered test light between KAPWR circuit and injector signal circuit at each injector harness connector. See CIRCUIT PIN IDENTIFICATION  table. Crank engine. If test light dimly glows while cranking, go to next step. If test light does not glow or glows brightly, replace PCM.
19. 46) Check Injector Flow
    
    Using Rotunda Fuel Injector Tester Cleaner (164-R3759), check flow rate of each injector. Replace any injectors that are not within leakage and flow specification. If all injectors are within leakage and flow specification, fault is intermittent. See TEST Z .